To study the predictive value of ALT, HBeAg and HBV DNA levels at baseline and HBV DNA levels at week 12 adefovir dipivoxil (ADV) treatment to the efficacy of it at week 52 in patients with HBeAg-positive chronic hepatitis B (CHB). Ninety-eight HBeAg-positive CHB patients with serum HBV DNA>or=1x10(6) copies/ml and ALT levels between 1.5 to 10 times of upper limits of normal (ULN) were enrolled in the study. Ten mg/d of ADV was administered for 52 weeks. Line serum samples were collected for measuring HBV DNA and HBV markers. The efficacy of the treatment at week 52 was evaluated in patients with different ALT, HBeAg and HBV DNA levels at baseline and HBV DNA levels at week 12 after treatment. At week 52 of ADV treatment, the rates of HBV DNA<10(3) were 72.7%, 66.7% and 53.0% respectively in patients with ALT>5xULN, HBeAg350 s/co (30.2%, P<0.01) and HBV DNA>10(8) copies/ml (34.4%, P<0.05) at baseline. HBeAg seroconversion rates were 42.2% and 7.5% (P<0.01) in patients with HBeAg titer350 S/co at baseline. In patients with HBV DNA<10(3), 10(3)-10(5) and >10(5) copies/ml at week 12, the ratios of them with HBV DNA<10(3) less than 1000 copies/ml at week 52 were 82.6%, 57.1% and 17.5% and significant differences were found between these groups (P<0.05); HBeAg seroconversion rates were 52.2%, 25.7% and 5.0% (P<0.05); ALT normalization rates were 100%, 83% and 75%, significantly higher in patients with HBV DNA<10(3) copies/ml than those with HBV DNA>10(5) copies/ml (P<0.05) at week 12. HBV DNA and HBeAg seroconversion at week 52 correlated with HBV DNA levels at week 12 (r=0.6 and r=0.5 respectively, P<0.01). In HBeAg-positive CHB patients treated with adefovir dipivoxil, HBV DNA levels at week 12 can be used to predict the efficacy at week 52. HBV DNA<10(3) copies/ml at week 12 predict a better treatment result at week 52.